#pragma once

#include <cassert>
#include "macros.h"

namespace base {

namespace subtle {

class RefCountedBase {
public:
  bool HasOneRef() const { return ref_count_ == 1; }

protected:
  RefCountedBase() : ref_count_(0) {}
  ~RefCountedBase() {}

  void AddRef() const { ++ref_count_; }

  // Returns true if the object should self-delete.
  bool Release() const {

    if (--ref_count_ == 0) {
      return true;
    }
    return false;
  }

private:
  mutable int ref_count_;
  DISALLOW_COPY_AND_ASSIGN(RefCountedBase);
};

class RefCountedThreadSafeBase {

public:
  bool HasOneRef() const;

protected:
  RefCountedThreadSafeBase();
  ~RefCountedThreadSafeBase();

  void AddRef() const;

  // Returns true if the object should self-delete.
  bool Release() const;

private:
  mutable int ref_count_;
  DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafeBase);
};

} // namespace subtle

template <class T> class RefCounted : public subtle::RefCountedBase {
public:
  RefCounted() {}

  void AddRef() const { subtle::RefCountedBase::AddRef(); }

  void Release() const {
    if (subtle::RefCountedBase::Release()) {
      delete static_cast<const T *>(this);
    }
  }

protected:
  ~RefCounted() {}

private:
  DISALLOW_COPY_AND_ASSIGN(RefCounted<T>);
};

// Forward declaration.
template <class T, typename Traits> class RefCountedThreadSafe;

// Default traits for RefCountedThreadSafe<T>.  Deletes the object when its ref
// count reaches 0.  Overload to delete it on a different thread etc.
template <typename T> struct DefaultRefCountedThreadSafeTraits {
  static void Destruct(const T *x) {
    // Delete through RefCountedThreadSafe to make child classes only need to be
    // friend with RefCountedThreadSafe instead of this struct, which is an
    // implementation detail.
    RefCountedThreadSafe<T, DefaultRefCountedThreadSafeTraits>::DeleteInternal(
        x);
  }
};

//
// A thread-safe variant of RefCounted<T>
//
//   class MyFoo : public base::RefCountedThreadSafe<MyFoo> {
//    ...
//   };
//
// If you're using the default trait, then you should add compile time
// asserts that no one else is deleting your object.  i.e.
//    private:
//     friend class base::RefCountedThreadSafe<MyFoo>;
//     ~MyFoo();
template <class T, typename Traits = DefaultRefCountedThreadSafeTraits<T>>
class RefCountedThreadSafe : public subtle::RefCountedThreadSafeBase {
public:
  RefCountedThreadSafe() {}

  void AddRef() const { subtle::RefCountedThreadSafeBase::AddRef(); }

  void Release() const {
    if (subtle::RefCountedThreadSafeBase::Release()) {
      Traits::Destruct(static_cast<const T *>(this));
    }
  }

protected:
  ~RefCountedThreadSafe() {}

private:
  friend struct DefaultRefCountedThreadSafeTraits<T>;
  static void DeleteInternal(const T *x) { delete x; }

  DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafe);
};

//
// A thread-safe wrapper for some piece of data so we can place other
// things in scoped_refptrs<>.
//
template <typename T>
class RefCountedData
    : public base::RefCountedThreadSafe<base::RefCountedData<T>> {
public:
  RefCountedData() : data() {}
  RefCountedData(const T &in_value) : data(in_value) {}

  T data;

private:
  friend class base::RefCountedThreadSafe<base::RefCountedData<T>>;
  ~RefCountedData() {}
};

} // namespace base

//
// A smart pointer class for reference counted objects.  Use this class instead
// of calling AddRef and Release manually on a reference counted object to
// avoid common memory leaks caused by forgetting to Release an object
// reference.  Sample usage:
//
//   class MyFoo : public RefCounted<MyFoo> {
//    ...
//   };
//
//   void some_function() {
//     scoped_refptr<MyFoo> foo = new MyFoo();
//     foo->Method(param);
//     // |foo| is released when this function returns
//   }
//
//   void some_other_function() {
//     scoped_refptr<MyFoo> foo = new MyFoo();
//     ...
//     foo = NULL;  // explicitly releases |foo|
//     ...
//     if (foo)
//       foo->Method(param);
//   }
//
// The above examples show how scoped_refptr<T> acts like a pointer to T.
// Given two scoped_refptr<T> classes, it is also possible to exchange
// references between the two objects, like so:
//
//   {
//     scoped_refptr<MyFoo> a = new MyFoo();
//     scoped_refptr<MyFoo> b;
//
//     b.swap(a);
//     // now, |b| references the MyFoo object, and |a| references NULL.
//   }
//
// To make both |a| and |b| in the above example reference the same MyFoo
// object, simply use the assignment operator:
//
//   {
//     scoped_refptr<MyFoo> a = new MyFoo();
//     scoped_refptr<MyFoo> b;
//
//     b = a;
//     // now, |a| and |b| each own a reference to the same MyFoo object.
//   }
//
template <class T> class scoped_refptr {
public:
  typedef T element_type;

  scoped_refptr() : ptr_(NULL) {}

  scoped_refptr(T *p) : ptr_(p) {
    if (ptr_)
      ptr_->AddRef();
  }

  scoped_refptr(const scoped_refptr<T> &r) : ptr_(r.ptr_) {
    if (ptr_)
      ptr_->AddRef();
  }

  template <typename U>
  scoped_refptr(const scoped_refptr<U> &r) : ptr_(r.get()) {
    if (ptr_)
      ptr_->AddRef();
  }

  ~scoped_refptr() {
    if (ptr_)
      ptr_->Release();
  }

  T *get() const { return ptr_; }

  // Allow scoped_refptr<C> to be used in boolean expression
  // and comparison operations.
  operator T *() const { return ptr_; }

  T *operator->() const {
    assert(ptr_ != NULL);
    return ptr_;
  }

  scoped_refptr<T> &operator=(T *p) {
    // AddRef first so that self assignment should work
    if (p)
      p->AddRef();
    T *old_ptr = ptr_;
    ptr_ = p;
    if (old_ptr)
      old_ptr->Release();
    return *this;
  }

  scoped_refptr<T> &operator=(const scoped_refptr<T> &r) {
    return *this = r.ptr_;
  }

  template <typename U> scoped_refptr<T> &operator=(const scoped_refptr<U> &r) {
    return *this = r.get();
  }

  void swap(T **pp) {
    T *p = ptr_;
    ptr_ = *pp;
    *pp = p;
  }

  void swap(scoped_refptr<T> &r) { swap(&r.ptr_); }

protected:
  T *ptr_;
};

// Handy utility for creating a scoped_refptr<T> out of a T* explicitly without
// having to retype all the template arguments
template <typename T> scoped_refptr<T> make_scoped_refptr(T *t) {
  return scoped_refptr<T>(t);
}
